When they were sworn in on July 29, Mayor Bloomberg hailed the current class of probationary firefighters. Two thirds of them represented minorities.

“This is, by any measure, an historic day for this department and for our entire city — and you are a true cross-section of New York,” Mr. Bloomberg told the probies.

Now the first court-ordered class of New York Fire Department recruits — the oldest and most diverse ever — is more than halfway through 18 weeks of training on Randall’s Island and there is reason for alarm at the Fire Academy.

The dropout rate among the original 318 recruits is reportedly about 15 percent . . . and climbing.

Traditionally, losses peak at about 10 percent.

Gone so far are about two dozen of 123 priority hires, mainly blacks and Hispanics in their 30s and 40s given a second chance at the FDNY after taking the 1999 or 2002 written exams that a federal judge ruled discriminatory.

Also reported to have dropped out are four of the eight women who had been undergoing Academy training.

Some may lament this development as a setback for diversity in the FDNY, but the rules must remain the same for everybody.

We urge the Fire Department to maintain its customary, rigorous physical and intellectual standards, despite the rash of dropouts and a flurry of injuries.

Highly trained and fully qualified members of the FDNY save the lives of New Yorkers virtually every day.

The clear and present need for diversity must not come at the expense of compromised standards.

Back in January 2010, U.S. District Court Judge Nicholas Garaufis ruled that the city had tolerated discrimination in the process of hiring firefighters.

It was the result of a federal equal employment opportunity complaint filed in 2002 by the Vulcan Society, a private organization of black firefighters. The judge’s finding was supported by the fact that, as of 2007, blacks made up 25.6 percent of the city’s population, but only 3.4 percent of the Fire Department’s ranks.

Judge Garaufis has described the FDNY as “a stubborn bastion of white male privilege.”

He decided that Fire Department’s entrance exams were discriminatory and ordered the city to create a new test that was not biased against minorities. He approved the revised written exam a year ago.

He had created a high-ranking FDNY position to oversee and strengthen the department’s minority recruiting and its diversity programs.

Only about 17 percent of those on the current roster of firefighters (excluding officers) are members of minorities. This figure includes: Hispanics (10 percent), blacks (6 percent), Asians (1 percent) and women (0.5 percent).

That’s why the city highly touted its current class of FDNY recruits as having 66-percent minority representation.

But passing the entrance exam is only the first step. Next come the rigors of the Fire Academy, which requires success both in instructional classes and physical training in order to graduate.

The Vulcan Society has raised concerns that instructors are making things too difficult for the current recruits. But Merit Matters, a group of anti-quota firefighters, says members of this class who don’t measure up should not be kept because of skin color or gender.

Ultimately, the No. 1 priority must be public safety. Considering all that is at stake, the Fire Academy is duty-bound to treat everyone equally and without discrimination.